1. Field of the Invention
The present invention relates to a continuous type automated apparatus for manufacturing a semiconductor device for forming a film on a wafer by a chemical vapor deposition (CVD) method.
2. Related Art
The CVD method, on a mass production scale, uses one of the following types of apparatus:
(1) batch type CVD apparatus, PA0 (2) continuous CVD apparatus including; PA0 (3) multi-chamber type CVD apparatus. PA0 (1) With the conveyor type, since the wafer moves and the heater 2 is fixed, it is difficult to measure the temperature of the wafer. Moreover, since the heater 2 underneath the conveyor belt 1 is installed apart from the conveyor belt 1 in some measure, it is impossible to control the temperature of the wafer precisely. PA0 (2) Also, as to the walking beam type, since the wafer is lifted from the wafer loading tables 6a to 6h while moving, it is unavoidable that the temperature of the wafer is lowered. Thus, the wafer is subject to a temperature cycle midway in film formation, and the film is sometimes thereby distorted. Since it is required to heat the wafer again so that the wafer temperature reaches a predetermined temperature when the wafer moves from the wafer loading table 6a to the next wafer loading table 6b, it takes time to stabilize the wafer temperature, thus complicating temperature adjustment.
(a) conveyor type, PA1 (b) walking beam type, and
The batch type CVD apparatus has a high mass- productivity, but is not suitable for a process increasing the diameter of a wafer or requiring precise production control of individual wafers. Moreover, its throughput is not high because of slow processing speed.
Further, a multi-chamber type CVD apparatus as shown in FIG. 11(c) is principally used for film formation under reduced pressure, and respective chambers are independent of one another. Therefore, various different processes are possible and flexibility is high, but the throughput is appreciably low.
Accordingly, when increase of the diameter of the wafer, high throughput and the like are required, the continuous type CVD apparatus is advantageous.
FIG. 10(a) illustrates a conveyor type continuous CVD apparatus, which is used principally for film formation under atmospheric pressure. Reference numeral 1 represents a conveyor belt, 2 represents a heater provided under the conveyor belt on which a film is formed on a wafer. Heater 2 is separated from the conveyor belt 1 and is stationary. A gas dispersion unit 3 is provided above the conveyor belt 1 and 4a and 4b represent cassette stations of a loader section and an unloader section. In such an apparatus, wafers are placed on the conveyor belt 1 and processed one after another. Further, since the heater 2 is installed stationary under the conveyor belt 1, the wafers are heated indirectly by radiation.
FIG. 10(b) illustrates a continuous type CVD apparatus of a walking beam system, which is used principally for film formation by a plasma CVD method and the like under reduced pressure. Reference number 5 represents a chamber, and 6a to 6h represent a plurality of wafer loading tables each equipped with a heater which are fixed to a base table 11. 7a to 7h represent eight walking beams arranged rotatably around the rotary shaft for holding the wafers, 8a and 8b represent gate valves, 9 represents a load lock chamber connected to the chamber 5 through gate the valve 8a, and 10 represents a cassette chamber connected to the load lock chamber 9 through the gate valve 8b.
To form a film on a wafer, a wafer is first loaded on the wafer loading table 6a in the chamber 5 from the load lock chamber 9, and heated to a predetermined temperature by means of a heater located underneath the wafer loading table 6a. Then, the wafer is held by the walking beam 7a after forming a film on the wafer located on the wafer loading table 6a, and is moved and loaded on the wafer loading table 6b where an additional film is formed. At this time, the next wafer is also loaded on the wafer loading table 6a in the chamber 5 from the load lock chamber 9, and heated to a predetermined temperature by a heater located underneath the wafer loading table 6a. Then, films are formed on the wafers at both wafer loading tables 6a and 6b.
The wafers are introduced into the chamber 5 in consecutive order in this manner, and films are formed continuously on the surfaces of the heated wafers at respective wafer loading tables 6a to 6h while moving the wafers in succession along fixed wafer loading tables 6a to 6h one after another. Accordingly, when a wafer completes a cycle from loading table 6a to loading table 6h, films of different types are formed as multiple layers or a film of a single layer having a predetermined film thickness is formed.
The above-described continuous type CVD apparatus has the following problems.
One solution to the foregoing might be to use a wafer holder fixed in position and equipped with a heater, in conjunction with a movable gas dispersion unit. However, it would no longer be possible to process the wafers continuously because the wafers do not move.
Therefore, it is an object of the present invention to solve the foregoing problems by providing an apparatus for manufacturing a semiconductor device in which the wafer can be moved while maintaining the wafer temperature at a predetermined temperature with which it is possible to control processing of each individual wafer and form multi-layer films of different types.